1. Field of the Invention
The present invention relates to an apparatus for and a method of detecting the shape of a solder portion. More particularly, it consists in a technique in which image data items obtained at different projection angles of light are combined, thereby to acquire image data having the features of the shape of a solder portion, and whether the shape of the solder portion is good or bad is judged on the basis of the acquired image data.
2. Description of the Prior Art
The shape of a solder portion for bonding the electrode of an electrical component to a substrate is generally detected by projecting light toward the solder portion and observing this solder portion with a camera. More specifically, the surface of the solder portion is a specular oblique surface. Accordingly, when the light is projected from above the solder portion and this solder portion is observed with the camera from above it, the light is reflected sidewards, and reflected light hardly enters the camera, so that the solder portion is observed dark. In the prior art, therefore, a detection area surrounding the solder portion is set, the number of pixels in black existing within the area is compared with a preset number by a computer, and whether the shape of the solder portion is good or bad is judged in accordance with the compared result.
Since, however, the prior-art method judges the quality of the shape of the solder portion on the basis of only the black information picked up by the camera, it is liable to misjudge due to the small amount of information on which the judgement is founded. As a concrete example, in a case where the camera has erroneously observed the surface of a resist sideward of the target solder portion without observing this solder portion, the method misjudges that the solder is sufficiently existent, because the resist surface is observed dark. Likewise, in a case where a light source is not lit up or where the substrate to be tested does not lie at a test position, the method has the problem of erroneously judging the sufficient existence of the solder, because a black image is picked up by the camera.